1. FIELD OF THE INVENTION
The present invention generally relates to a joint between adjacent concrete slabs for overcoming existing problems which occur due to large scale relative movement of adjacent concrete slabs which results from the slabs shrinking when aging. More specifically, a resilient finger joint for concrete slabs is provided which allows and adjusts for relative vertical movement of adjoining slabs with the joint including an arrangement for absorbing vibrations and impact loads encountered which result from traffic passing over the joint between adjacent slabs. The joint includes a plurality of fingers supported by a resilient bed. The fingers are positioned in staggered, interdigitated relation and each finger is associated with an anchor alongside of and partially overlapping one end of the adjacent finger with a pivot pin or shaft interconnecting the anchors and fingers with each finger including an end that is free of an opposing anchor but supported by the resilient bed. The anchors are retained in place by a bonding material which surrounds the anchor and bonds it to an adjoining concrete slab with the bonding material serving as a portion of a traffic bearing surface between the concrete slabs and the finger/anchor assembly.
2. Description Of The Prior Art
Various types of joints between slabs have been provided but generally have failed to effectively solve the edge problems associated with joints between adjacent concrete slabs. Elastic fillers, metal sliding plates and metal finger joints have been utilized in joints between adjacent concrete slabs and generally have been found to be too expensive or otherwise impractical. One of the more successful arrangements has been the use of metallic finger plates which supposedly allow retention of the surface plane of the slabs over the joint without any uneven surfaces thereby eliminating bumps that might occur when traffic passes over the joint. The traffic is borne by the individual fingers which in many cases remain sufficiently parallel to the concrete surface to function. However, in many other cases, the edges of the concrete slab curl and the fingers which are, in effect, extensions of the concrete slab, also move relative to the designed plane surface of the slab and because the fingers extend from the slab, edge curling of the slab causes the ends of the cantilevered fingers to move relatively more than the slab itself. Further, the metallic fingers are rigidly attached to the slab and the fastening system which holds them in place is subject to the vibration an significant mechanical stresses which occur when the traffic crosses the joint since the cantilever loads imparted to the fingers by vehicular traffic are quite destructive with a relatively large number of the fingers in such installations breaking away from the concrete slabs.
The following U.S. patents disclose the state of the art in this field of endeavor.
U.S. Pat. No. 2,207,085 PA1 U.S. Pat. No. 2,263,824 PA1 U.S. Pat. No. 2,743,652 PA1 U.S. Pat. No. 3,217,614 PA1 U.S. Pat. No. 3,698,292 PA1 U.S. Pat. No. 4,504,170
None of the rigid systems have a mechanism which allows the system to adjust to the relative vertical movements of the adjoining slabs and none of the systems have means for absorbing vibrations and impact loads from traffic. Further, none of the prior art utilizes a plurality of interdigitated fingers mounted in a resilient bed combined with anchors which pivotally support one end of the fingers with a bonding material forming a traffic bearing surface between the plane surface of adjacent concrete slabs by forming a continuous surface with the slab and fingers as disclosed in this application.